PCPlus 326: Turing and his machines

In August last year, I read Alan Turing: The Enigma by Andrew Hodges, which turned out to be an excellent biography of Alan Turing, especially so since 2012 was the centenary of his birth (I’d bought the Centenary Edition). Hodges is a mathematician and I certainly appreciated the way he described Turing’s inventions and mathematical insights. Despite (or in spite of) that, Hodges detailed Turing’s life and death in great detail, without causing the reader to flag and get bored. The description of the war years were extremely interesting, and the book contains the best account of the cracking of the Enigma Machine I have read anywhere. And, as always, whenever I read about Turing’s final days, I get angry at the mores and laws of the 50s (which, if you think about it, is a bit futile: it was what it was).

So, what better way for me to (a) celebrate Turing’s impact on the burgeoning computer world, and (b) commemorate the demise of PCPlus than to write a brief biography and a description of Turing’s greatest abstract invention: his machines and how he used them to prove Hilbert’s Entscheidungsproblem or decision problem.

(Note: back when I wrote about my previous article, I said I never received the PDF copy of my final article for PCPlus. Turns out, all I had to do was ask for it. So here it is.)

(I used to write a monthly column for PCPlus, a computer news-views-n-reviews magazine in the UK, which sadly is no longer published. The column was called Theory Workshop and appeared in the Make It section of the magazine. When I signed up, my editor and the magazine were gracious enough to allow me to reprint the articles here after say a year or so.)